1. Field of the Invention
The present invention generally relates to measuring air quality using a sensor, and, more particularly, to a system and method for measuring air quality using a micro-optical mechanical gas sensor.
2. Description of the Related Art
There is growing public awareness and concern about the adverse effects of indoor air quality on human health and productivity in public buildings, work places and personal dwellings. Media attention concerning toxic mold and related health effects as well as the outbreak of infectious diseases such as SARS has led to renewed attention to indoor air quality in homes, commercial buildings, schools and hospitals. See Instrument Society of America (ISA), “Air-Pollution Sensors Forecast 25% Growth by 2003”, InTech, September, 1999.
Current commercial air quality monitoring devices are large expensive analytical instruments, such as mass spectrometers and spectroscopes, that are often restricted to monitoring a small number of atmospheric pollutants. Each type of device has its advantage and disadvantages. For example, optical absorption spectroscopy devices are sensitive and selective, but are expensive and non-robust. Electrochemical/electroadsorptive devices, although inexpensive and portable, typically are limited to sensing only one gas. Mass spectroscopy devices are sensitive, but are expensive and requires vacuum technology. Finally, chromatography devices are sensitive, but expensive, non-portable, and non-robust.
A variety of methods are available for simultaneously detecting a number of components in a gas mixture. For example, Raman spectroscopy, Fourier Transform Infrared (“FTIR”) spectroscopy, and mass spectroscopy may be used. While these methods have their merits, they also have their drawbacks. Cumbersome vacuum technology, an essential part of mass spectroscopy, limits its portability. FTIR spectroscopy typically employs absorption spectroscopy, which, in order to achieve high sensitivity, requires the use of some form of White cell, see White, J. U., J. Opt. Soc. Am. 32,285 (1942), where pathlengths of up to kilometers may be attained. See Hanst, P. L., “Pollution: Trace Gas Analysis” in “Fourier Transform Infrared Spectroscopy”, etd. J. R. Ferraro & L. J. Basile, vol. 2, 79-110, Academic Press, Inc. (1979). The use of some form of White cell restricts ruggedness since careful alignment of the infrared beam entering and leaving the cell is required.